BMW's 7 Series luxo-limo will receive its first extensive update next year, however these spy images of a 7 Series development mule show that we shouldn't expect much in the way of exterior changes.

Instead, for their midlife update the F01 and F02 7 Series will feature a raft of under-the-skin revisions that will aim to boost power and efficiency.

The turbocharged 3.0 litre six-cylinder petrol of the 740i could jump from 240kW to 260kW, and the 750i's 4.4 litre twin-turbo V8's output may rise to 335kW - an increase of 35kW.

Currently, only the V12-powered 760Li flagship utilises an eight-speed automatic, however BMW's latest version of its eight-speed is expected to be bolted to I6 and V8 variants from 2013.

The almost complete absence of camouflage on this development car (very unusual for a BMW prototype) suggest that the car's sheetmetal will carry over unchanged, with only minor alterations to the front and rear bumpers.

New wheel designs should be offered though, and the headlamp clusters will likely make greater use of LED technology.

Inside, there appears to be no substantial design changes. However, expect more up-to-date electronic equipment to feature in the 2013 7 Series' cabin.